a) Field of the Invention
The present invention relates to a semiconductor device and its manufacture method, and more particularly to a semiconductor device and its manufacturing method capable of changing a wiring pattern once formed.
b) Description of the Related Art
Interconnections of a semiconductor device change in various ways depending upon circuit function of the device. if design of a semiconductor integrated circuit device starts after the circuit structure is decided, a turn-around time from a user order to final products becomes long.
Most of circuits in a semiconductor integrated circuit device have often the same fundamental structures. Therefore, if interconnections of a semiconductor device can be changed in various ways so as to satisfy the circuit function to be manufactured, the turn-around time of semiconductor devices can be shortened and considerable merits are given to both manufacturers and users.
Techniques for cutting an interconnection once formed are known, for example, cutting a fuse by flowing an excess current therethrough or applying an energy beam such as laser thereto.
For example, fine patterning with a focused ion beam (FIB) utilizes sputtering phenomenon which occurs when an ion beam is applied to the surface of a device in vacuum. By utilizing this phenomenon, an opening can be formed through a protective film on an interconnection and cut the interconnection.
It is also possible to connect electrically separated interconnections with a metal film which is formed by applying an ion beam while source gas is blown on the surface of the device in a vacuum chamber.
Another method is also known by which two superposed metal wiring layers separated by an insulating film are connected by applying a laser beam to the superposed area (Japanese Patent Laid-open Publication Hei 6-112321).
Of these techniques of connecting electrically separated two interconnections, the former technique requires a vacuum atmosphere and a supply of source gas to the device, and the latter technique requires forming two interconnections to be connected in two different layers.
In connecting electrically separated interconnections by the FIB method, it is necessary to form an opening, blow source gas, and radiate an ion beam, respectively in vacuum.
With the method described in Japanese Patent Laid-open Publication Hei 6-112321 for connecting superposed two metal wiring layers, even if interconnections can be formed in one layer, two-layer interconnections are required in order to form a superposed area to provide interconnection changeability.